insanity (n.) Look up insanity at Dictionary.com
1580s, "state of being insane, seriously impaired state of mental functioning," from Latin insanitatem (nominative insanitas) "unhealthfulness, unsoundness, disease," noun of quality from insanus "mad, insane; outrageous, excessive" (see insane). Meaning "extreme folly" is from 1844. The Latin abstract noun was insania ""unsoundness of mind, madness, frenzy."